Calcium and Magnesium Levels in Agricultural Soil and Sewage Sludge in an Industrial Area from Southeastern Spain: Relationship with Plant (Saccharum officinarum) Disposition

Abstract

This investigation was initiated to assess the following objectives: (1) to measure the total calcium and magnesium content in agricultural soil and sewage sludge from the Mediterranean coastal area of Motril (southeastern Spain); (2) to determine the pH values of indicated samples in order to evaluate first their influence on calcium and magnesium content, and second on levels of these minerals in the main crop (sugar cane: Saccharum officinarum) grown in the area; (3) to study the influence of industrial activities, first on calcium and magnesium cantents and pH values in agricultural soil, and second on calcium and magnesium concentrations present in sugar cane samples; (4) to check if the calcium and magnesium levels existing in agricultural soil exert any influence on corresponding element uptake by sugar cane plants. Calcium levels found in agricultural soil were significantly higher (p < 0.05) than those found in sewage sludge. Significant linear relationships between calcium and magnesium concentrations in agricultural soil and sewage sludge (p < 0.005) were found. Calcium concentrations found in soil from the industrialized area (39.2 ± 7.2 mg g−1) were significantly higher than those corresponding to the non-industrialized area (31.0 ± 6.6 mg g−1). The pH values determined in agricultural soil were significantly influenced by industrial activity (p < 0.05). The industrial activity and pH values measured in agricultural soil did not statistically influence either calcium or magnesium levels in the sugar cane plants. Calcium and magnesium concentrations existing in agricultural soil did not significantly influence the element uptake by sugar cane plants.